1. Field of the Invention
This invention relates generally to an off-set printing machine for printing a continuous web or slip, and more particularly to such a printing machine incorporating means for adjusting the positions of plate, blanket and impression cylinders relative to one another.
2. Prior Art
Conventionally, the printing of business forms has been carried out by high-speed business form-printing rotary presses.
Such a business form-printing rotary press is quite large in size and requires much time for the exchange of printing patterns and adjustments. Further, during the time when the necessary adjustments are made for the pattern exchange, a large loss of the printing sheet is produced. To overcome these difficulties, various handy printing machines or presses have been proposed, particularly for the printing of a small lot of a continuous slip.
Generally, with such business form-printing machines, the plate, blanket and impression cylinders do not need to be exchanged in accordance with the size of the printing sheet to be used. In such example as disclosed in Japanese Kokai No. 62-64552, a continuous printing sheet is supplied between a pair of opposed, rotating blanket and impression cylinders, and one of the blanket and impression cylinders is brought into engagement with the other at a predetermined timing, so that a continuous printing sheet (continuous slip) is intermittently fed at such predetermined timing to effect the printing. Another example is known in which recesses or notches, formed respectively in peripheral surfaces of the blanket and impression cylinders, are circumferentially displaced with respect to each other to change the amount of feed of the printing sheet, so that the printing sheet is intermittently fed a required amount to print the printing sheet.
A conventional off-set printing machine of the latter type includes three gears 1a, 2a and 3a mounted respectively on plate, blanket and impression cylinders 1, 2 and 3, as shown in FIG. 1. When a recess 2b in the peripheral surface of the blanket cylinder 2 is circumferentially displaced with respect to a recess 3b in the peripheral surface of the impression cylinder 3, as shown in FIGS. 2A and 2B, a recess 1b in the peripheral surface of the plate cylinder 1 must also be circumferentially displaced with respect to the recess 2b of the blanket cylinder 2 by an amount corresponding to the amount of displacement of the recess 2b from the recess 3b. To achieve this position adjustment, the gears 1a and 2a are rotatably mounted on the plate and blanket cylinders 1 and 2, respectively, and are normally fixed or coupled by suitable fastening means to the respective cylinders 1 and 2 for rotation therewith. On the other hand, the gear 3a is fixedly mounted on the impression cylinder 3 for rotation therewith. The adjustment of the position of the plate cylinder 1 relative to the blanket cylinder 2 is necessitated because when it is desired to print a printing pattern j smaller in size than the maximum printing surface i of each cylinder (FIGS. 2A and 2B), a smudge 4 of the ink on the plate cylinder on the trailing side 5 of the printing plate (not shown) is transferred to the printing surface of the blanket cylinder 2 as at 6 (FIG. 3). As a result, the smudge 6 on the blanket cylinder 2 is transferred to the continuous printing sheet 7 as shown in FIG. 3, which adversely affects the quality of the printed material.
Also, in an off-set printing machine of this general type, the above-mentioned smudge 4 on the trailing side of the printing plate is unavoidable since the printing is carried out, maintaining a well-balanced relation between the ink and water. To solve this problem, conventionally, the arc spanned by the recess 1b of the plate cylinder 1 has been made smaller than that of the recess 2b of the blanket cylinder 2, as shown in FIG. 4.